Many different industries require power supplies for supplying constant power based on a three-phase power source.
Cyclo-converters have been developed for use in efficient power supplies in order to provide a number of improvements over conventional rectifier power supplies and two stage power supplies.
A cyclo-converter provides an efficient single stage power converter. A benefit of adopting single stage power conversion is based on the fact that a single stage converter will have an efficiency similar to the efficiency of either of the individual stages of a conventional two-stage rectifier (e.g. 96%). In other words the losses from a single-stage converter are only half of that of a two-stage converter. This greater efficiency (lower losses) leads to a corresponding decrease in the size of components within the rectifier and hence a smaller product that costs less to produce. Other benefits are obtained by virtue that the exhaust air heat from the converter will be lower for a given system power (easing power system design) and in the fact that a single-stage converter can be realised with considerably fewer components than a conventional two-stage rectifier design.
The present applicants have developed a unique three-phase resonant cyclo-converter configuration as described in PCT publication WO2008/018802, which is hereby incorporated by reference.
This present application relates to an improved method (and associated control system) for controlling a three-phase resonant cyclo-converter, such as the type described in WO2008/018802. It will be appreciated that although power converters such as those described in WO2008/018802 are particularly useful in the telecommunication industry that they may also equally be applicable in other industries.
WO2008/018802 has suggested that proportional and integral feedback elements based on the measured output voltage of the cyclo-converter may be used to control the cyclo-converter's switching frequency. These proportional and integral feedback elements may enable the switching frequency to be adjusted so that the output voltage of the cyclo-converter may be adjusted accordingly.
Embodiments of the present invention provide an improved mechanism for controlling a three phase resonant cyclo-converter switching frequency throughout the full phase of an input power signal.
An object of the present invention is to provide improved control over existing three-phase resonant cyclo-converters.
A further object of the present invention is to provide improved control of a three-phase resonant cyclo-converter over the full phase of an input power signal.
Each object is to be read disjunctively with the object of at least providing the public with a useful choice.
The present invention aims to overcome, or at least alleviate, some or all of the afore-mentioned problems.